Vector tetraquark state candidates: Y(4260 / 4220), Y(4360 / 4320), Y(4390) and Y(4660 / 4630)

In this article, we construct the C ⊗ γ _μ C and Cγ ₅ ⊗ γ ₅γ _μ C type currents to interpolate the vector tetraquark states, then carry out the operator product expansion up to the vacuum condensates of dimension-10 in a consistent way, and obtain four QCD sum rules. In calculations, we use the formula μ =√M²Y-(2Mc)² to determine the optimal energy scales of the QCD spectral densities, moreover, we take the experimental values of the masses of the Y(4260 / 4220), Y(4360 / 4320), Y(4390) and Y(4660 / 4630) as input parameters and fit the pole residues to reproduce the correlation functions at the QCD side. The numerical results support assigning the Y(4660 / 4630) to be the C ⊗ γ _μ C type vector tetraquark state cc̄ss̄ , assigning the Y(4360 / 4320) to be Cγ ₅ ⊗ γ ₅γ _μ C type vector tetraquark state cc̄qq̄ , and disfavor assigning the Y(4260 / 4220) and Y(4390) to be the pure vector tetraquark states.